Process control chart warning results. Bars indicate the number of days prior to failure that an action level threshold was first triggered for each of the monitored steering coil parameters. A - High Alarm triggered indicating parameters exceeding ± 6 standard deviations of the mean weekly sample value. B - Low alarm indicating the observation of nine consecutive weekly samples on one side of the mean. C - Low alarm indicating the observation of two out of three consecutive weekly samples greater than two standard deviations from the mean but not exceeding the high alarm limit.